So I've ordered Cali a 5 gallon tank (waiting for delivery), and I was thinking about getting her some cherry shrimps to live with. I've been researching them, of course, but was curious if anyone here had any input on keeping shrimp, with or without bettas...

And, if anyone could tell me the best way to oxygenate the water, without A) sucking the shrimp into a filter, or B) causing a hideous current, I'd very much appreciate it, since I haven't found an answer to this anywhere...

I don't know much about shrimps (other than they taste good ), but I can give you some ideas for oxygenating the water. I like to use sponge filters for my betta tanks. These filters force air through a sponge, and as the air is moving to the top of the tank, bring up water from the bottom. It's a very tiny current and the sponge acts as a platform for the beneficial bacteria. The bubbles oxygenate the water without causing a torrent. I have these filters on all of my betta tanks are they are gentle enough for even the long fins of my rosetail.